[imp] How to add "Add Reply-To" to compose window

[Jean Charles Delépine]

Hello,

I can't find a way to add a button "Add Reply-To" near the "Add Cc"  
and "Add Cci" in compose window.

Is there any option/configuration I miss ?

One tipical usage of the Reply-To header : mail sent with many person  
in Cc but want the answers go
only to me, or only to an alias, or ...

Sincerly,
       Jean Charles Delépine